Activated zeolite - suitable carriers for microorganisms in anaerobic digestion processes?

Plant cell wall structures represent a barrier in the biodegradation process to produce biogas for combustion and energy production. Consequently, approaches concerning a more efficient de-polymerisation of cellulose and hemicellulose to monomeric sugars are required. Here, we show that natural activated zeolites (i.e. trace metal activated zeolites) represent eminently suitable mineral microhabitats and potential carriers for immobilisation of microorganisms responsible for anaerobic hydrolysis of bio- polymers stabilising related bacterial and methanogenic communities. A strategy for comprehensive analysis of immobilised anaerobic populations was developed that includes the visualisation of biofilm formation via scan- ning electron microscopy and confocal laser scanning microscopy, community and fingerprint analysis as well as enzyme activity and identification analyses. Using SDS polyacrylamide gel electrophoresis, hydrolytical ac- tive protein bands were traced by congo red staining. Liquid chromatography/mass spectroscopy revealed cellulo- lytical endo- and exoglucanase (exocellobiohydrolase) as well as hemicellulolytical xylanase/mannase after proteolytic di- gestion. Relations to hydrolytic/fermentative zeolite colonis- ers were obtained by using single-strand conformation polymorphism analysis (SSCP) based on amplification of bacterial and archaeal 16S rRNA fragments. Thereby, domi- nant colonisers were affiliated to the genera Clostridium, Pseudomonas and Methanoculleus. The specific immobilisa- tion on natural zeolites with functional microbes already